Emulsifying activities

Inert matrix with emulsified active component... 

Emulsified active component trapped in carrier skeleton... 

Inert matrix with emulsified active component occasionally protected by nylon gauze or cellophane foil... 

A well-studied example of a bioemulsifier is emulsan, a cell surface-exposed molecule that allows Acinetobacter calcoaceticus RAG-1 to attach to crude oil droplets [123]. Upon depletion of the short-chain alkanes utilised by this strain, the emulsan molecules were released from the bacterial surface, thereby allowing the cells to leave the oil droplet and to find a new substrate. Important positive side-effects of this mechanism seem to be that the remaining emulsan hydrophilises the droplet and prevents both the reattachment of A. calcoaceticus RAG-1 and the coalescence of the used oil droplet with other droplets that still contain unexploited alkanes. Bredholt et al. [124] studied the oil-emulsifying activity of Rhodococcus sp. strain 094. When exposed to inducers of crude-oil emulsification, the cells developed a strongly hydrophobic character, which was rapidly lost when crude-oil emulsification started. This indicated that the components responsible for the formation of cell-surface hydrophobi-city acted as emulsion stabilisers after release from the cells. 

Toren, A., Navon-Venezia, S., Ron, E. Z. and Rosenberg, E. (2001). Emulsifying activities of purified alasan proteins from Acinetobacter radioresistens KA53, Appl. Environ. Microbiol., 67, 1102-1106. 

The present study was conducted to obtain additional information on changes in soy protein subunits during limited proteolysis. Enzymatic soy protein deamidation that occurred, in addition to limited proteolysis, during germination of soybean seeds was investigated. The effects of proteolysis and deamidation on solubility and emulsifying activity were compared. Phosphorylation of soy protein with a commercially available protein kinase and its effects on subsequent changes in functional properties of the protein were also studied. 

Functionality Analysis. Solubility was determined on 1% (w/v) dispersion of protein in 0.2 M phosphate buffers at a pH of 3.0 to 8.0. After stirring for 0.5 hr, the dispersion was filtered (0.45 /xm. Millipore), and the filtrate was analyzed for protein by the BCA method (21). Emulsifying activity index (EAI), expressed as interfacial area/unit weight protein (mVg) / was assessed by the turbidometric method of Pearce and Kinsella (22). 

Emulsifying activity index (EAI) is a measure of the ability of protein to emulsify oil, which depends on solubility, size, charge, and surface activity of the protein molecules. The effect of proteolysis with pronase E on EAI of the modified protein was relatively insignificant (Figure 6) However, deamidation appeared to enhance EAI, especially at pH values more basic than the isoelectric point (pH 4.7). 

Figure 6. Emulsifying activity index of soy proteins as a function of pH. Intact soy protein (O) soy protein proteolyzed with pronase E for 1 h (V) and 3 h ( ) deamidated soy protein ( ).

In limited proteolysis, proteases such as pronase E hydrolyzed the 7S subunits of soy proteins more than the IIS subunits, resulting in enhanced protein solubility. Deamidation with relatively insignificant peptide bond hydrolysis that occurred during the germination of soybeans imparted to the storage protein improved solubility and emulsifying activity. On the other hand, the incorporation of phosphorus in soy proteins by the protein kinase cAMPdPK was too low to effect significant... 

Effective Hamaker constant, 234 Emulsifying activity index, 186,188/ Emulsions, concentrated oil-in-water, effea of interdroplet forces on centrifugal stability, 229-245 Enhancers of taste. See Taste enhancers Enzymatic modification of soy proteins, 181-190... 

Figure 7. Emulsifying activity (expressed as volume percentage of the emulsified layer) of pepsin hydrolysates of soy protein as a function of pH and hydrolysis time. No hydrolysis (A) 2 h ( ) 8 h (X) 17 h ( ) 24h(O) (39).

Cameron, D.R., Weber, M.E., Idziak, E.S, Neufeld, R.J., and Cooper, D.G. 1991. Determination of interfacial areas in emulsions using turbidimetric and droplet size data Correction of the formula for emulsifying activity index. J. Agric. Food Chem. 39 655-659. 

Emulsifying activity index The turbidity of a dilute emulsion is Emulsifying activity index... 

EAI. see Emulsifying activity index El. see Electron impact ionization Elasticity, gel rheology tests, see also Viscoelasticity... 

Emulsifying activity index (EAI), protein analysis, 297 (table)... 

Addition of potassium chloride may be omitted if the chloro-sulfonyl isocyanate is free of sulfur trioxide. Otherwise, traces of sulfur trioxide will give rise to a yellow or brown coloration of the reaction mixture and to formation of small amounts of byproducts which, because of their emulsifying activity, may interfere with further processing. 

The emulsifier activity of culture broth was determined according to Cooper and Goldenberg (30). Four milliliters of cell-free culture samples was added to 6 mL of kerosene, vigorously mixed with a vortex for 2 min, and left undisturbed to stand for 24 h at room temperature. The E24 is given as a percentage of the height of emulsified layer (cm) divided by the total height of the liquid column (31). 

Figure 5 shows some data referring to the ability of biosurfactant to emulsify kerosene produced by B. subtilis ATCC 6633 at the different substrate concentrations tested (5, 10, 20, and 40 g/L). Besides a decrease in surface tension, stabilization of hydrocarbon/water is frequently used as an indicator of surface activity. Note, however, that the quantity of biosurfactant produced should not be related to the E24 because that is an intrinsic property of the molecule. A similar behavior of the emulsifying activity in relation to the carbon source concentration and to the incubation period has been observed. The diverse initial concentrations of commercial sugar studied favor the formation of a surface-active compound, with an emulsifying activity >50% in a 48-h process. The maximum values for emulsion activity of 57.9 and 56.9% were determined for 10 and 20 g/L of substrate, respectively. It should be emphasized that there was a reduction in the E24 after a 96-h period of incubation. Carvalho et al. (36) reported similar results for cell-free fermented broth by Bacillus sp. emulsified in kerosene. 

The effective utilization of proteins in food systems is dependent on tailoring the protein s functional characteristics to meet the complex needs of the manufactured food products. Many food proteins require modification to improve such functional properties as solubility, foaming and emulsifying activity (EA). Reviews on classical food protein modifications for improved functionality are available in the literature (Means and Feeney, 1971 Feeney and Whitaker, 1977, 1982, 1986). 

The emulsifying activity index (EAI) curves for phosphorylated whole casein solution versus pH showed shift of their minima towards the acid... 

FIG. 3. Emulsifying activity index of native ( ) and phosphorylated whole caseins [4 (O) 7 ( ) and 11 (V) mol P/mol protein]. (Source From Haertle and Chobert (1999), by courtesy of Food Nutrition Press, Inc.)... 

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